The present invention broadly relates to the art of fluid delivery systems and, more particularly, to a combination shut-off and excess flow valve for use in association along transmission lines of such systems.
The present invention relates generally to fluid delivery systems. It finds particular application in conjunction with underground gas distribution systems and will be described with particular reference thereto. However, it is to be appreciated that the invention is equally applicable for use in other environments, including above-ground installations, such as in industrial and/or commercial buildings, for example. Additionally, the present invention is particularly well suited for use with non-bypass type excess flow valves. However, it is to be distinctly understood that bypass type excess flow valves can also be used without departing from the principles of the present invention.
Shut-off valves and excess flow valves are each well known and commonly used in gas distribution systems. Typically, a shut-off valve is installed along a gas delivery line adjacent the connection or tie-in of the same with a main supply line. Such shut-off valves are commonly buried under ground in a small box or vault and are normally accessible through a pipe or passage extending from the ground surface down to the actuation feature of the valve. The shut-off valve can be displaced between open and closed positions using a suitable long-handled wrench or other device that is extended down through the passage to engage the actuation feature of the valve. As such, where repairs or other modifications are being made downstream along the delivery line, the shut-off valve is routinely closed to terminate gas flow along the downstream portion of the delivery line.
When used, an excess flow valve of either the bypass or non-bypass type is typically installed along a gas delivery line downstream of the shut-off valve. The excess flow valve acts to shut off the flow of gas through the delivery line where a break occurs in the delivery line, such as due to third party damage or a natural disaster, for example. Typically, the excess flow valve is buried in the ground and is not accessible without excavation. Bypass type excess flow valves are adapted to allow the passage of a small amount of gas, usually less than 20 CFM, even though the valve has been tripped and remains closed. This allows the bypass-type excess flow valve to automatically reset when the line pressure on both sides of the valve becomes substantially equalized. Where a non-bypass excess flow valve is used, the repaired line is re-pressurized using an external pressure source. This is commonly done by supplying compressed air or another gas from a point upstream of the excess flow valve, typically at the gas meter. While both types of excess flow valve have been successfully used for a considerable period of time, certain disadvantages have been perceived that have reduced the adoption and wide spread installation of excess flow valves. One of the primary perceived disadvantages is that there is no external indicator of the condition (i.e., open or closed position) of an installed excess flow valve.
In an attempt to overcome this perceived disadvantage associated with the use of traditional excess flow valves, combination shut-off and excess flow valves have been devised. One such valve is disclosed in Saarem, et al., U.S. Pat. No. 6,003,550, for example. In Saarem, a valve body is rotatably supported on a housing, and an excess flow valve is disposed along a passage through the valve body. The valve body is rotatable between a first flow position, a second shut-off position oriented at an angle of about 90 degrees from the first position and a third position for resetting a tripped excess flow valve that is oriented at an angle of about 180 degrees from the first position.
In operation, the Saarem valve is set in the first position and the excess flow valve operates in a traditional manner. When an excess flow condition occurs, the excess flow valve trips or closes substantially preventing the flow of gas therethrough. The valve body can thereafter be moved to the shut-off position while repairs are made to the distribution line. Once the repairs are complete, the valve can be moved to the third, reset position in which the flow of gas along the line causes the excess flow valve to return to its open position. The valve must then be returned to its first position in which the excess flow valve is in the proper orientation relative to the fluid flow direction along the line to operate in a typical manner. One significant disadvantage of such valves, however, is that if the valve is left in the third, resetting position, the excess flow valve will remain open regardless of the flow conditions. As such, a repair technician who is unsure of which direction the valve was initially in and/or is inattentive in resetting the valve may inadvertently leave the valve in the reset position.